A regional ocean model is used to evaluate the roles of wind, surface heat flux, and basin-scale climate variability in regulating the upwelled nitrate supply in the California Current. A strong positive trend in nitrate flux from 1980 to 2010 was driven almost entirely by enhanced equatorward winds, negating a weak negative trend associated with increased surface heat flux. Increased upwelling and nitrate flux are consistent with cooler surface temperatures and higher phytoplankton concentrations observed over the same period. Changes in remote ocean forcing, resulting primarily from basin-scale climate variability (e.g., El Niño–Southern Oscillation and Pacific Decadal Oscillation), drive considerable interannual fluctuations and may dominate the ecosystem response on interannual to decadal time scales. However, comparison with previously published findings suggests that local wind intensification persists through changing basin-scale climate regimes. Understanding the different time scales of variability in forcing mechanisms, and their interactions with each other, is necessary to distinguish transient ecosystem impacts from secular trends.